The purpose of this project is to elucidate the detailed molecular events that take place during contraction and relaxation of heart muscle. The basic approach is to isolate and purify the contractile proteins, then study the interaction of mixtures of purified proteins. The biochemical and physical properties of column-purified dog cardiac myosin will be investigated. The aggregation and enzymatic properties of single-headed cardiac myosin, prepared by proteolytic digestion, will be compared to those of conventional myosin. We will look for the presence of "C-protein", shown to be involved in myosin aggregation, in cardiac myosin preparations. If present, the protein will be purified and its aggregation effect will be studied. We will continue development of our television scanner system for the analytical ultra-centrifuge, concentrating on the development of a pulsed system for multicell operation and the extension of operating wavelengths into the 220-280nm range.